html, body {
    height: 100%;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #f0f0f0;
}
#gameArea {
    width: 400px;
    height: 400px;
    background-color: black;
    position: relative;
    box-shadow: 0 0 20px rgba(0,0,0,0.5);
}
.snake {
    width: 20px;
    height: 20px;
    background-color: lime;
    position: absolute;
    /* 添加霓虹效果 */
    box-shadow: 0 0 5px lime, 0 0 20px lime, 0 0 30px lime, 0 0 40px lime;
}

.apple {
    width: 20px;
    height: 20px;
    background-color: red;
    position: absolute;
    /* 添加霓虹效果 */
    box-shadow: 0 0 5px red, 0 0 20px red, 0 0 30px red, 0 0 40px red;
}